Flashlights generally include a battery chamber having an end cap for retaining one or more batteries, a light bulb electrically connected to the one or more batteries and a reflector for reflecting light from the light bulb in a particular direction. The electrical connection between the batteries and the light bulb usually includes a switch mechanism for selectively providing electrical energy from the batteries to the light bulb and, therefore enabling the flashlight to be turned on and off. The primary function of flashlights is to provide a convenient portable storable light source which is capable of projecting light in a particular direction.
Some flashlights are capable of focusing and defocusing light projected by the flashlight by allowing the light bulb to be moved within the reflector along the reflector's optical axis. The reflector is typically a parabolic shaped reflector because such a reflector provides a theoretical focus of the light when the light bulb is positioned at the parabolic reflector's focal point. In this regard, light rays emanating from a light bulb positioned at the focal point of a parabolic reflector are reflected parallel to the parabolic reflector's optical axis. Referring to FIG. 1A, a light beam dispersion is shown from a parabolic reflector with a light bulb positioned at the focal point of the parabolic reflector. In contrast, as shown in FIG. 1B, when the light bulb is moved away from the parabolic reflector's focal point, light rays reflected by the parabolic reflector diverge (i.e., defocus) leaving a glaring light void about the center of the reflected light rays and decreasing the light gathered from the light bulb.
The electrical energy to enable a flashlight to operate is usually provided by one battery, or two or more batteries in series arrangement, held within the battery chamber of the flashlight. When the charge in the batteries is depleted, a user will typically replace the batteries by removing the end cap, removing the old batteries from the battery chamber, inserting new batteries into the battery chamber, and replacing the end cap. However, when replacing multiple batteries in a flashlight, the possibility arises that a user may improperly position the batteries in a nonseries arrangement. For example, a user may improperly align the new batteries such that the positive poles of the batteries face each other, or may commingle the old batteries with the new batteries and misalign a new battery with an old battery. Misaligning the batteries may have undesired consequences, for example explosion causing physical injury, to a user of the flashlight.
Additionally, batteries often naturally emit hydrogen gas. As such, when batteries are contained within the flashlight's battery chamber, the possibility arises that hydrogen gas emitted by the batteries may become trapped within the flashlight. In some circumstances, a defective battery will emit high quantities of hydrogen gas. As a consequence, hydrogen gas may accumulate within the flashlight, thus raising the possibility of undesired consequences to a user of the flashlight, for example explosion causing physical injury.
Finally, parts of the flashlight sometimes require replacement. For example, the flashlight's light bulb will require replacement when the light bulb's filament burns out, which is often discovered when the flashlight is needed (e.g., when there are no other sources of light, including for example electrical power outages which occur at night or darkness when camping outdoors). Flashlights usually include a spare light bulb positioned on the interior of the end cap. Replacing a burned out bulb with a bulb positioned on the end cap is difficult, especially in low or no light conditions. For example, during a power outage, replacing the light bulb in a typical flashlight would require a user to remove the end cap, locate and grasp a small spare light bulb on the end cap without allowing the batteries to fall out of the flashlight, replace the end cap, remove the head assembly, replace the burned out bulb and replace the head assembly, all in darkness.